A man pushes a shopping cart across a level floor. What force resists the effort force? A) gravity B) friction C) the normal for
1 answer:
Answer:
B) Friction
Explanation:
Friction is a force that acts when an object is sliding along a surface. Microscopically, this force is due to the fact that the two surfaces are not perfectly smooth, but they have "imperfections" that cause a force that opposes the motion of the object.
For an object sliding on a flat surface, the force of friction has magnitude:
where
is the coefficient of kinetic friction
m is the mass of the object
g is the acceleration of gravity
The direction of the force of friction is always opposite to the direction of motion of the object.
In reality, friction also acts if the object is at rest and it is pushed by a force; in this case, we talk about static friction, and its magnitude is
where is called coefficient of static friction, and it is generally larger than the coefficient of kinetic friction.
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, we find the total angular displacement:
2) If we put larger tires, with radius
, the angular displacement will be smaller. We can see this by using the same formula. In fact, this time we have:
where S is the arc length and r is the radius. The problem says that the truck drove for 2600 m, so this corresponds to the total arc length covered by the tire:
2) If we put larger tires, with radius